Passivated Emitter and Rear Cell Silicon Solar Cells with a Front Polysilicon Passivating Contacted Selective Emitter

Abstract

p‐Type silicon solar cells with a structure of passivated emitter and rear cell (PERC) are a mainstream product of the photovoltaic (PV) industry. Because of its low cost, PERC technology will continue to be dominant for a long time. One of the key features to improve PERC solar cell performance is the use of a selective emitter (SE), which is now mainly realized by laser doping (LD). However, SE by LD still cannot perfectly resolve recombination underneath the front metallized area. The use of a tunnel oxide passivated contact (TOPCon) can dramatically reduce recombination at the metallized area. With the help of an organic mask and etching by texturing solution, the TOPCon SE structure on PERC cells is realized. An average efficiency of 22.65% is reached on 6 in., commercial grade p‐type Czochralski wafers. The average open‐circuit voltage of PERC cells with TOPCon SE is 14.6 mV higher than LD SE. However, the short‐circuit current is lowered by parasitic absorption of polysilicon of alignment margins, which makes cell efficiency of the two SE structures almost the same. With improved alignment precision, TOPCon SE will provide an increase in efficiency.

TOPerc Solar Cell: An Integral Approach of Tunnel Oxide Passivated Contact (TOPCon) and Passivated Emitter and Rear Contact (PERC) Architectures for Achieving Efficiency Beyond 25%

“…Step 2: Now this 17 μm  17 μm device (Figure 3b) is scaled by 100 along Y-axis and also scaled by 100 along X-axis which is the [10][11][12] unit cell (Figure 3a). During scaling, each layer is considered by "entity list."…”

“…Then boron is diffused on the rear side. After that the rear side is masked with stearic acid, [ 10 ] antiacid paste, [ 11 ] and thick oxide layer using UV laser. [ 12 ] The uncovered poly‐Si regions on rear side may be etched by KOH solution [ 10 ] or HF/HNO 3 solution [ 11 ] or TMAH [ 12 ] using a single‐side etcher after that masks are removed.…”

“…After that the rear side is masked with stearic acid, [ 10 ] antiacid paste, [ 11 ] and thick oxide layer using UV laser. [ 12 ] The uncovered poly‐Si regions on rear side may be etched by KOH solution [ 10 ] or HF/HNO 3 solution [ 11 ] or TMAH [ 12 ] using a single‐side etcher after that masks are removed. Then the front side is masked with stearic acid, [ 10 ] antiacid paste, [ 11 ] and thick oxide layer using UV laser.…”

“…There are very few literatures where they have fabricated p-PERC and n-TOPCon with passivated front contact but not achieved substantial performance. [10][11][12] Yuan et al fabricated p-PERC with passivated front contacts and achieved an efficiency of 22.6% on a large area mono CZ wafer. [10] However, for further improvement of efficiency the rear contacts also may be passivated (Figure 1c).…”

“…[10][11][12] Yuan et al fabricated p-PERC with passivated front contacts and achieved an efficiency of 22.6% on a large area mono CZ wafer. [10] However, for further improvement of efficiency the rear contacts also may be passivated (Figure 1c). The structures of Figure 1 are simulated using Sentaurus technology computer-aided design (TCAD) simulation software.…”