Role of the Front Electron Collector in Rear Emitter Silicon Heterojunction Solar Cells

Abstract

Front electron collectors in rear emitter hydrogenated amorphous silicon/crystalline silicon (a-Si:H/c-Si) solar cells are comprehensively investigated with the objective of increasing cell power conversion efficiency. Since such cells benefit from the lateral electron conductivity of the n-doped substrate, the electrical constraint on the front transparent conductive oxide (TCO) layer is relaxed. However, cell improvement is only expected if the front side is optimized. Here, we present our understanding of recombination losses in the front amorphous silicon layers and at the a-Si:H/c-Si interface, which determine the short-circuit current. In addition, we show how the TCO/(n + i)a-Si:H/(n)c-Si contact has to be finely engineered to minimize the resistance for electrons to be extracted. Both points are addressed through experimental and simulation works.

High-efficiency crystalline silicon solar cells: status and perspectives

“…With this technology it is also fairly straightforward to change the polarity of the device. 46,162,243,244 Due to the asymmetric band offsets at the amorphous/crystalline silicon interface, holes usually face a larger barrier than electrons, potentially hindering efficient carrier collection (see Fig. 9).…”

Homo-heterojunction concept: From simulations to high efficiency solar cell demonstration

“…For a better readability and analysis of the lifetime curves at both low and high injection conditions, Fig. 4 summarizes the values of effective lifetime at an excess carrier density of 10 15 First of all, by comparing the results of SHJ REF and SHJ 950°C we note that τ LIL is slightly increased after annealing whatever the passivation system. Such improvement probably originates from oxygen-related phenomena in the c-Si wafer.…”

“…Thus, the (i) and (p) a-Si:H layer thicknesses are optimized for the compromise between passivation (low interface defect density D it ), doping (strong field effect) and vertical conduction. Additionally, the role of the transparent conductive oxide (TCO) [14,15] is required to collect laterally the charges (to insure low lateral series resistances) and to achieve an effective Metal/TCO/(i/p) a-Si:H/c-Si contact (correlated to vertical series resistance) [16].…”

Heterojunction solar cells with 23% efficiency onn-type epitaxial kerfless silicon wafers

“…The cells in this study had an emitter on the back side, which was the side opposite to the illuminated side . For the conventional front‐emitter HJ structure, the p ‐layer thickness is determined considering the absorption loss and electrical properties of the p ‐layer.…”

“…In this work, we aimed to the efficiency of epi‐Si HJ solar cells by reducing SFs and applying a rear‐emitter structure . We performed spatial current density ( J ) mapping of epi‐Si HJ solar cells by spectral response mapping (SR‐MAP).…”