Title :
Improved Rear Surface Passivation of Cu(In,Ga)Se
Solar Cells: A Combination of an Al
Author :
Vermang, B. ; Fjällström, Viktor ; Xindong Gao ; Edoff, M.
Author_Institution :
Dept. of Eng. Sci., Uppsala Univ., Uppsala, Sweden
Abstract :
An innovative rear contacting structure for copper indium gallium (di) selenide (CIGS) thin-film solar cells is developed in an industrially viable way and demonstrated in tangible devices. The idea stems from the silicon (Si) industry, where rear surface passivation layers are combined with micron-sized local point contacts to boost the open-circuit voltage (VOC) and, hence, cell efficiency. However, compared with Si solar cells, CIGS solar cell minority carrier diffusion lengths are several orders lower in magnitude. Therefore, the proposed CIGS cell design reduces rear surface recombination by combining a rear surface passivation layer and nanosized local point contacts. Atomic layer deposition of Al2O3 is used to passivate the CIGS surface and the formation of nanosphere-shaped precipitates in chemical bath deposition of CdS to generate nanosized point contact openings. The manufactured Al2O3 rear surface passivated CIGS solar cells with nanosized local rear point contacts show a significant improvement in VOC compared with unpassivated reference cells.
Keywords :
alumina; atomic layer deposition; copper compounds; gallium compounds; indium compounds; liquid phase deposition; passivation; point contacts; semiconductor thin films; solar cells; ternary semiconductors; thin film devices; Al2O3; CIGS solar cell; Cu(InGa)Se2; atomic layer deposition; cell efficiency; chemical bath deposition; copper indium gallium selenide thin-film solar cells; nanosized local rear point contacts; nanosized point contact openings; nanosphere-shaped precipitates; open-circuit voltage; rear surface passivation layer; rear surface recombination; Aluminum oxide; Passivation; Photovoltaic cells; Silicon; Standards; Substrates; Al$_{2}$O$_{3}$ ; Cu(In,Ga)Se$_{2}$, Ga grading; atomic layer deposition; copper indium gallium selenide (CIGS); nanosized; passivated emitter; passivated emitter and rear cell (PERC); photovoltaics; point contact openings rear locally diffused cell (PERL); rear surface passivation, Si; solar cells; thin film;
Journal_Title :
Photovoltaics, IEEE Journal of
DOI :
10.1109/JPHOTOV.2013.2287769