High Efficiency Current-Matched III–V/n-TOPCon Tandem Solar Cell With System-Level Energy Output and Loss Analysis

Abstract

This study reports a current-matched two-terminal (2T) tandem solar cell comprising a GaInP/GaAs/InGaAs triple-junction III–V top cell with a fully back-metalized commercial device efficiency of 29.96%. This top cell is integrated with an n-type tunnel oxide passivated contact (n-TOPCon) silicon bottom cell, which delivers an efficiency of 22.03%. To mitigate the photon transmission barrier imposed by the fully back-metalized III–V structure, we first optimize the silicon bottom cell area, achieving an efficiency of 27.41% with current matching at 14.4 cm². A further enhancement is realized by introducing rear-side albedo illumination (0.3 sun) while maintaining equal top and bottom cell areas as 12.04 cm², resulting in a significantly improved tandem efficiency of 35.33% with J_sc = 13.03 mA cm⁻², V_oc = 3.58 V, and FF = 75.70%. These experimentally obtained electrical parameters for the Si, III–V, and III–V/Si tandem devices were individually used as inputs in PVsyst simulation software for a 1 MW photovoltaic system. The tandem configuration delivers an annual energy output of 1222.1 MWh to the grid with a performance ratio (PR) of 0.920, surpassing standalone Si and III–V modules. System-level loss analysis showed Si modules exhibited higher thermal and LID losses, while III–V suffered greater voltage degradation from temperature effects. Furthermore, the tandem configuration exhibited reduced spectral, thermal, mismatch, and wiring losses with stable inverter output demonstrating a practical strategy for high-efficiency tandem photovoltaics.