• A Review on TOPCon Solar Cell Technology
    Hasnain Yousuf, Muhammad Quddamah Khokhar, Sanchari Chowdhury, Duy Phong Pham, Youngkuk Kim, Minkyu Ju, Younghyun Cho, Eun-Chel Cho, Junsin Yi
    The tunnel oxide passivated contact (TOPCon) structure got more consideration for development of high performance solar cells by the introduction of a ... + READ MORE
    The tunnel oxide passivated contact (TOPCon) structure got more consideration for development of high performance solar cells by the introduction of a tunnel oxide layer between the substrate and poly-Si is best for attaining interface passivation. The quality of passivation of the tunnel oxide layer clearly depends on the bond of SiO in the tunnel oxide layer, which is affected by the subsequent annealing and the tunnel oxide layer was formed in the suboxide region (SiO, Si2O, Si2O3) at the interface with the substrate. In the suboxide region, an oxygen-rich bond is formed as a result of subsequent annealing that also improves the quality of passivation. To control the surface morphology, annealing profile, and acceleration rate, an oxide tunnel junction structure with a passivation characteristic of 700 mV or more (Voc) on a p-type wafer could achieved. The quality of passivation of samples subjected to RTP annealing at temperatures above 900°C declined rapidly. To improve the quality of passivation of the tunnel oxide layer, the physical properties and thermal stability of the thin layer must be considered. TOPCon silicon solar cell has a boron diffused front emitter, a tunnel-SiOx/n+-poly-Si/ SiNx:H structure at the rear side, and screen-printed electrodes on both sides. The saturation currents Jo of this structure on polished surface is 1.3 fA/cm2 and for textured silicon surfaces is 3.7 fA/cm2 before printing the silver contacts. After printing the Ag contacts, the Jo of this structure increases to 50.7 fA/cm2 on textured silicon surfaces, which is still manageably less for metal contacts. This structure was applied to TOPCon solar cells, resulting in a median efficiency of 23.91%, and a highest efficiency of 24.58%, independently. The conversion efficiency of interdigitated back-contact solar cells has reached up to 26% by enhancing the optoelectrical properties for both-sides-contacted of the cells. - COLLAPSE
    September 2021
  • Secondary Phase and Defects in Cu2ZnSnSe4 Solar Cells with Decreasing Absorber Layer Thickness
    Young-Ill Kim, Dae-Ho Son, Jaebaek Lee, Shi-Joon Sung, Jin-Kyu Kang, Dae-Hwan Kim, Kee-Jeong Yang
    The power conversion efficiency of Cu2ZnSnSe4 (CZTSe) solar cells depends on the absorber layer thickness; however, changes in the ... + READ MORE
    The power conversion efficiency of Cu2ZnSnSe4 (CZTSe) solar cells depends on the absorber layer thickness; however, changes in the characteristics of the cells with varying absorber layer thickness are unclear. In this study, we investigated the changes in the characteristics of CZTSe solar cells for varying absorber layer thickness. Five absorber thicknesses were employed: CZTSe1 2.78 μm, CZTSe2 1.01 μm, CZTSe3 0.55 μm, CZTSe4 0.29 μm, and CZTSe5 0.15-0.23 μm. The efficiency of the CZTSe solar cells decreased as the absorber thickness decreased, resulting in power conversion efficiencies of 10.45% (CZTSe1), 8.67% (CZTSe2), 7.14% (CZTSe3), 3.44% (CZTSe4), and 1.54% (CZTSe5). As the thickness of the CZTSe absorber layer decreased, the electron-hole recombination at the grain boundaries and the absorber-back-contact interface increased. This caused an increase in the current loss, owing to light loss in the long-wavelength region. In addition, as the thickness of the CZTSe absorber layer decreased, more ZnSe was produced, and the resulting defects and defect clusters led to an open-circuit voltage loss. - COLLAPSE
    September 2021
  • Characterization of an In2Se3 Passivation Layer for CIGS Solar Cells with Cd-free Zn-containing Atomic-layer-deposited Buffers
    Suncheul Kim, Ho Jin Lee, Byung Tae Ahn, Dong Hyeop Shin, Kihwan Kim, Jae Ho Yun
    Even though above 22% efficiencies have been reported in Cd-free Cu(In,Ga)Se2 (CIGS) solar cell with Zn-containing buffers, the ... + READ MORE
    Even though above 22% efficiencies have been reported in Cd-free Cu(In,Ga)Se2 (CIGS) solar cell with Zn-containing buffers, the efficiencies with Zn-containing buffers, in general, are well below 20%. One of the reasons is Zn diffusion from the Zn-containing buffer layer to CIGS film during buffer growth. To avoid the degradation, it is necessary to prevent the diffusion of Zn atoms from Zn-containing buffer to CIGS film. For the purpose, we characterized an In2Se3 film as a possible diffusion barrier layer because In2Se3 has no Zn component. It was found that an In2Se3 layer grown at 300°C was very effective in preventing Zn diffusion from a Zn-containing buffer. Also, the In2Se3 had a large potential barrier in the valence band at the In2Se3/CIGS interface. Therefore, In2Se3 passivation has the potential to achieve a super-high efficiency in CIGS solar cells that employ Cd-free ALD processed buffers containing Zn. - COLLAPSE
    September 2021
  • Development of Wireless IoT Sensors for Individual Photovoltaic Module Monitoring

    태양광 모듈 개별 모니터링을 위한 무선 IoT센서

    Jongsung Park, Changheon Kim, Jiwon Lee, Jihyun Kim, Sanghyuk Yoo, Bum Seung Yang

    박종성, 김창헌, 이지원, 김지현, 유상혁, 양범승

    In order to perform photovoltaic (PV) operation and management (O&M) efficiently, individual PV module monitoring is becoming more important. In this research ... + READ MORE
    In order to perform photovoltaic (PV) operation and management (O&M) efficiently, individual PV module monitoring is becoming more important. In this research, we developed wireless IoT sensor which can monitor individual photovoltaic modules. This IoT sensor can detect the output voltage, current and module temperature of individual modules and provide monitored data by wireless communication. Measured voltage error was 1.23%, and it shows 16.6 dBM, 0.42sec and 7.1 mA for voltage, transmittance output, response time and mean power consumption, respectively. IoT sensors were demonstrated in the test field with real climate environment condition and each of 5 sensors showed precise results of voltage, current and temperature. Also, sensors were compared with commercial power-optimizers and showed result difference within 5%. - COLLAPSE
    September 2021