Latest developments in CdTe, CuInGaSe2 and GaAs/AlGaAs thin film PV solar cells

I.M. Dharmadasa 한국물리학회 2009 Current Applied Physics Vol.9 No.2

This paper summarises the latest developments in thin film solar cells based on CdTe, CuInGaSe2 and GaAs/AlGaAs absorber materials. After proposing a new model for CdS/CdTe solar cells, new designs based on graded bandgap multi-layer solar cells have been proposed for photovoltaic (PV) solar cell development. These new designs have been tested with well researched materials, GaAs/AlGaAs, and highest open circuit voltages of 1170 mV and fill factors of ~0.85 values were produced for initial growths and fabrications. This work has led to the identification of disadvantages of the tunnel junction approach, in the present manufacturing process. Recently, it has been shown that Fermi level pinning takes place at one of the four experimentally observed defect levels in CuInGaSe2/metal interfaces very similar to that of CdTe/metal contacts. These levels are at 0.77, 0.84, 0.93 and 1.03 eV with ±0.02 eV error and are situated above the valence band maximum. As a result, discrete values of open circuit voltages are observed and the situation is very similar to that of CdS/CdTe solar cells. It is becoming clear that Fermi level pinning due to defect levels dominates the performance in at least CdTe and CIGS thin film devices and future research should be directed to solving associated issues and hence improving the performance of PV solar cells. This paper summarises the latest developments in thin film solar cells based on CdTe, CuInGaSe2 and GaAs/AlGaAs absorber materials. After proposing a new model for CdS/CdTe solar cells, new designs based on graded bandgap multi-layer solar cells have been proposed for photovoltaic (PV) solar cell development. These new designs have been tested with well researched materials, GaAs/AlGaAs, and highest open circuit voltages of 1170 mV and fill factors of ~0.85 values were produced for initial growths and fabrications. This work has led to the identification of disadvantages of the tunnel junction approach, in the present manufacturing process. Recently, it has been shown that Fermi level pinning takes place at one of the four experimentally observed defect levels in CuInGaSe2/metal interfaces very similar to that of CdTe/metal contacts. These levels are at 0.77, 0.84, 0.93 and 1.03 eV with ±0.02 eV error and are situated above the valence band maximum. As a result, discrete values of open circuit voltages are observed and the situation is very similar to that of CdS/CdTe solar cells. It is becoming clear that Fermi level pinning due to defect levels dominates the performance in at least CdTe and CIGS thin film devices and future research should be directed to solving associated issues and hence improving the performance of PV solar cells.

3-5족 적층형과 CuInGa(S,Se)2 및 Cu2ZnSn(S,Se)4 화합물반도체 박막태양전지

정연길 ( Yonkil Jeong ),박동원 ( Dong Won Park ),이재광 ( Jae Kwang Lee ),이재영 ( Jaeyoung Lee ) 한국공업화학회 2015 공업화학 Vol.26 No.5

신 기후변화대응(Post 2020)을 위한 대체에너지의 역할과 더불어 태양전지의 중요성이 높아져 가고 있다. 태양전지의 종류는 크게 재료관점에서 보면 유기물과 무기물 계열로 구분할 수 있지만 대규모 발전역할에서는 현재까지 실리콘과 같이 양산성과 안정성 기반의 무기물 태양전지가 주된 역할을 하고 있다. 특히 최근 몇 년간 화합물반도체 태양전지에 대한 연구는 급속도로 가속화되면서 3-5족 적층형 태양전지, chalcopyrite 계열 CuInGa(S,Se)2 (CIGSSe) 태양전지와 kesterite 계열 Cu2ZnSn(S,Se)4 (CZTSSe) 태양전지 연구가 대표적으로 주류를 이루어 왔다. 따라서 화합물반도체 태양전지에서 주류를 이루고 있는 3-5족 적층형, CIGSSe 및 CZTSSe 태양전지들의 연구개발동향 및 기술적인 주요내용들에 대해 소개하고자 한다. Solar cells with other alternative energies are being importantly recognized related with post-2020 climate change regime formation. In a point of view of materials, solar cells are classified to organic and inorganic solar cells which can provide a plant-scale electricity. In particular, recent studies about compound semiconductor solar cells, such as III-V tandem solar cells, chalcopyrite-series CIGSSe solar cells, and kesterite-series CZTSSe solar cells were rapidly accelerated. In this report, we introduce a research trend and technical issues for the compound semiconductor solar cells.

고효율 적층형 태양전지를 위한 유무기 페로브스카이트

박익재(Ik Jae Park),김동회(Dong Hoe Kim) 한국세라믹학회 2019 세라미스트 Vol.22 No.2

To overcome the theoretical efficiency of single-junction solar cells (> 30 %), tandem solar cells (or multi-junction solar cells) is considered as a strong nominee because of their excellent light utilization. Organic-inorganic halide perovskite has been regarded as a promising candidate material for next-generation tandem solar cell due to not only their excellent optoelectronic properties but also their bandgap-tune-ability and low-temperature processpossibility. As a result, they have been adopted either as a wide-bandgap top cell combined with narrow-bandgap silicon or CuIn x Ga (1-x) Se 2 bottom cells or for all-perovskite tandem solar cells using narrow- and wide-bandgap perovskites. To successfully transition perovskite materials from for single junction to tandem, substantial efforts need to focus on fabricating the high quality wide- and narrow-bandgap perovskite materials and semi-transparent electrode/recombination layer. In this paper, we present an overview of the current research and our outlook regarding perovskite-based tandem solar technology. Several key challenges discussed are: 1) a wide-bandgap perovskite for top-cell in multi-junction tandem solar cells; 2) a narrow-bandgap perovskite for bottom-cell in allperovskite tandem solar cells, and 3) suitable semi-transparent conducting layer for efficient electrode or recombination layer in tandem solar cells.

Atomically Thin-Layered Molybdenum Disulfide (MoS₂) for Bulk-Heterojunction Solar Cells

Singh, Eric,Kim, Ki Seok,Yeom, Geun Young,Nalwa, Hari Singh American Chemical Society 2017 ACS APPLIED MATERIALS & INTERFACES Vol.9 No.4

<P>Transition metal dichalcogenides (TMDs) are becoming significant because of their interesting semiconducting and photonic properties. In particular, TMDs such as molybdenum disulfide (MoS2), molybdenum diselenide (MoSe2), tungsten disulfide (WS2), tungsten diselenide (WSe2), titanium disulfide (TiS2), tantalum sulfide (TaS2), and niobium selenide (NbSe2) are increasingly attracting attention for their applications in solar cell devices. In this review, we give a brief introduction to TMDs with a focus on MoS2; and thereafter, emphasize the role of atomically thin MoS2 layers in fabricating solar cell devices, including bulk-heterojunction, organic, and perovskites-based solar cells. Layered MoS2 has been used as the hole-transport layer (HTL), electron-transport layer (ETL), interfacial layer, and protective layer in fabricating heterojunction solar cells. The trilayer graphene/MoS2/n-Si solar cell devices exhibit a power-conversion efficiency of 11.1%. The effects of plasma and chemical doping on the photovoltaic performance of MoS2 solar cells have been analyzed. After doping and electrical gating, a power-conversion efficiency (PCE) of 9.03% has been observed for the MoS2/h-BN/GaAs heterostructure solar cells. The MoSrcontaining perovskites-based solar cells show a PCE as high as 13.3%. The PCE of MoS2-based organic solar cells exceeds 8.40%. The stability of MoS2 solar cells measured under ambient conditions and light illumination has been discussed. The MoS2-based materials show a great potential for solar cell devices along with high PCE; however, in this connection, their long-term environmental stability is also of equal importance for commercial applications.</P>

Determination of the lateral collection length of charge carriers for silver-nanowire-electrode-based Cu(In,Ga)Se₂ thin-film solar cells

Lee, Sangyeob,Jang, Jiseong,Cho, Kyung Soo,Oh, Yong-Jun,Hong, Ki-Ha,Song, Soomin,Kim, Kihwan,Eo, Young-Joo,Ho Yun, Jae,Gwak, Jihye,Chung, Choong-Heui Elsevier 2019 Solar energy Vol.180 No.-

<P><B>Abstract</B></P> <P>Silver nanowire (AgNW) electrodes have been employed in solar cells as transparent conducting electrodes (TCEs). When a AgNW electrode is used as a network-type TCE in solar cells, photogenerated charge carriers must laterally travel to reach AgNW networks. If the empty space of the network is larger than the lateral collection length of the charge carriers ( <SUB> L lc </SUB> ), a significant fraction of the charge carriers will be lost. Therefore, determination of <SUB> L lc </SUB> is essential for choosing and/or designing a suitable network for solar cells. Here, we develop a method to relate the lateral photocurrent measured from a specially designed pattern to the <SUB> L lc </SUB> value. We apply this method to Cu(In,Ga)Se<SUB>2</SUB> thin-film solar cells with AgNW TCEs. The <SUB> L lc </SUB> value was determined to be ≈ 26 μm in the CdS/CIGS/Mo structure under 1-sun illumination. The measured lateral collection length is much larger than the normal spacing between AgNWs, indicating a high lateral collection efficiency in AgNW TCE-based CIGS thin-film solar cells.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Lateral collection length is important for network-electrode-based solar cells. </LI> <LI> A method to determine the lateral collection length is developed. </LI> <LI> The lateral collection length for Cu(In,Ga)Se<SUB>2</SUB> solar cells was 26 μm under 1-sun. </LI> <LI> The method can be aaplied to other solar cells with network-transparent-electrodes. </LI> </UL> </P>

Flexible p-type PEDOT:PSS/a-Si:H hybrid thin film solar cells with boron-doped interlayer

Lee, Yoo Jeong,Yeon, Changbong,Lim, Jung Wook,Yun, Sun Jin Elsevier 2018 SOLAR ENERGY -PHOENIX ARIZONA THEN NEW YORK- Vol.163 No.-

<P><B>Abstract</B></P> <P>We reported highly flexible a-Si:H thin film solar cells with p-type poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) window. We firstly adopted the substrate-type cell structure on 75 μm-thick polyimide (PI) film unlike earlier studies in which the superstrate-type cell structures were utilized and the deformation of PEDOT:PSS was inevitably caused by subsequent deposition processes. We clearly demonstrated that the performance of the hybrid a-Si:H thin film solar cells with the substrate-type structure was superior to that of the superstrate-type cells. A highly boron-doped interlayer (IL) of 5 nm thickness was introduced at the hetero-interface between the p-type PEDOT:PSS and intrinsic a-Si:H to enhance built-in potential and form a homogeneous p/i-junction in the cell, which led to further improvement in the cell performance. The efficiencies of the cells with the PEDOT:PSS/IL window on glass and PI substrates were 7.40% and 6.52%, respectively, which were considerably higher than that of the cell with a conventional p-type microcrystalline (μc-) Si:H window. Also, the degradation of the cell with PEDOT:PSS window by bending was much smaller than the cell with p-type μc-Si:H window, particularly at bending radius < 10 mm. The present work demonstrates that PEDOT:PSS with a proper interfacial layer is a promising p-type window for substrate-type a-Si:H thin film solar cells and also for enhancing the flexibility of inorganic light absorbing materials-based solar cells on flexible film substrates.</P> <P><B>Highlights</B></P> <P> <UL> <LI> p-Type PEDOT:PSS windows were used for flexible a-Si:H thin film PV cells. </LI> <LI> PEDOT:PSS should be free from a damage caused by subsequent deposition process. </LI> <LI> Surfactant addition and H<SUB>2</SUB>-treatment improve the adhesion of PEDOT:PSS on a-Si:H. </LI> <LI> Insertion of highly B-doped Si leads to further improvement in cell performances. </LI> <LI> Cell with PEDOT:PSS showed higher flexibility than cell with p-type μc-Si:H particularly at bending radius < 10 mm. </LI> </UL> </P>

Improved adhesion of multi-layered front electrodes of transparent a-Si:H solar cells for varying front colors

Lee, Da Jung,Lim, Jung Wook,Shin, Myunghun,Kim, Gayoung,Yun, Sun Jin Elsevier 2018 Solar Energy Materials and Solar Cells Vol.183 No.-

<P><B>Abstract</B></P> <P>A low temperature deposition process was developed to fabricate ultra-thin, transparent, multi-layered electrodes (TMEs) suitable to be used on variously shaped flexible substrates, as those utilized in the transparent solar cells of building-integrated photovoltaic (BIPV) systems. The fabricated TMEs consisted of a bottom layer (BL) of gallium doped zinc oxide (GZO), an Ag-layer, and optoelectronic-controlling layers (OCLs) of GZO; and exhibited a high transmittance of 90% at 550 nm, and a low sheet resistance of 9.4 Ω/sq. at the thickness of ~ 100 nm. Because the Ag of TMEs easily detach from inorganic or amorphous surfaces, the GZO-BL was chemically treated in a diluted acetic and nitric acid mixture (10:2) to generate changes in its surface energy and improve the Ag adhesion. To quantitatively evaluate the Ag adhesion of TMEs, we proposed and conducted a tape pull-out adhesion test, and found the optimum GZO-BL texturing condition. The developed TMEs were used as the front transparent conductive electrodes of transparent a-Si:H solar cells to tune their reflection colors. By changing the thickness of the OCL, a wide range of colors was obtained without serious efficiency variations, as was predicted by optical simulations. The fabricated transparent cells show a high efficiency of 4.8%, as well as a high average transmittance of ~ 20% in the visible range. The developed TME structure, using the proposed deposition process, can be fabricated on various substrates and can be applied to devices that require a variety of colors such as BIPVs, wearable PVs, and the PVs of moving vehicles.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We use ultra-thin transparent multi-layered electrodes of a-Si:H solar cells. </LI> <LI> They exhibit a high transmittance of 90%, and a low sheet resistance of 9.4 Ω/sq. </LI> <LI> To improve adhesion, chemically surface-treatment is carried out on GZO (BL) layer. </LI> <LI> Various colors are implemented without serious reduction of cell efficiency. </LI> <LI> The solar cells show a high efficiency and transmittance of 4.8% and ~ 20%. </LI> </UL> </P>

Recent Development of P-Tunnel Oxide Passivated Contact Solar Cells

( Yang Zhao ),( Muhammad Quddamah Khokhar ),( Hasnain Yousuf ),( Xinyi Fan ),( Seungyong Han ),( Youngkuk Kim ),( Suresh Kumar Dhungel ),( Junsin Yi ) 한국전기전자재료학회 2023 전기전자재료학회논문지 Vol.36 No.4

Crystalline silicon solar cells have attracted great attention for their various advantages, such as the availability of raw materials, high-efficiency potential, and well-established processing sequence. Tunnel oxide passivated contact (TOPCon) solar cells are widely regarded as one of the most prospective candidates for the next generation of high-performance solar cells because an efficiency of 26% has been achieved in small-area solar cells. Compared to n-type TOPCon solar cells, the photo conversion efficiency (PCE) of p-type TOPCon is slightly higher. The highest PCEs of p-type TOPCon and n-type TOPCon solar cells are 26.0% and 25.8%, respectively. Despite the highest efficiency in small-area cells, limited progress has been achieved in p-type TOPCon solar cells for large are due to their lower carrier lifetime and inferior surface passivation with the boron-doped c-Si wafer. Nevertheless, it is of great importance to promoting the p-type TOPCon technology due to its lower price and well-established manufacturing procedures with slight modifications in the PERC solar cells production lines. The progress in different approaches to increase the efficiencies of p-type TOPCon solar cells has been reported in this review article and is expected to set valuable strategies to promote the passivation technology of p-type TOPCon, which could further increase the efficiency of TOPCon solar cells.

고집광 태양전지의 비균등 조사에 의한 출력특성

신구환(Shin Goo-Hwan),유광선(Ryu Kwanosun),차원호(Cha Won-Ho),명로훈(Myung Noh-Hoon),김용식(Kim Young-Sik),강기환(Kang Gi-Hwan) 한국태양에너지학회 2011 한국태양에너지학회 학술대회논문집 Vol.2011 No.4

A solar cell is primary parts to produce electrical energy from the Sun. And, we can utilize those solar cells as a power generation system in home, factory, and so on. In order to make proper power, the solar cells are configured in series and parallel laydown. In condition of uniform illumination, the solar array will produce an enough power by photovoltaic effects from the solar cells. In case of non-uniform illumination on the solar cells, the power will be dramatically decreased compared to design. Fortunately, there were so many research outputs regarding the illumination effects on solar array. In this work, we tried to find out the non-uniform effects on unit CPV solar cell, because there were no research outputs for unit CPV solar cell considering illumination. The CPV solar cell was used in CPV system to make a power by the Sun. We chosen the triple junction solar cell of GaAsInP2Ge for simulation, which has a 30 % of conversion efficiency. By simulation, we obtained the output performance of CPV solar cells in condition of various illumination by using Hamming Window function. Its performance was degraded by 10 % to 50 % depending illumination conditions.

New Generation Multijunction Solar Cells for Achieving High Efficiencies

이선화,박진주,김영국,김상호,S. M. Iftiquar,이준신 한국태양광발전학회 2018 Current Photovoltaic Research Vol.6 No.2

Multijunction solar cells present a practical solution towards a better photovoltaic conversion for a wider spectral range. In this review, we compare different types of multi-ijunction solar cell. First, we introduce thin film multijunction solar cell include to the thin film silicon, III-V material and chalcopyrite material. Until now the maximum reported power conversion efficiencies (PCE) of solar cells having different component sub-cells are 14.0% (thin film silicon), 46% (III-V material), 4.4% (chalcopyrite material) respectively. We then discuss the development of multijunction solar cell in which c-Si is used as bottom sub-cell while III-V material, thin film silicon, chalcopyrite material or perovskite material is used as top sub-cells.