We propose a heterojunction bipolar transistor (HBT) architecture for solar cell using earth-abundant CBTSSe, CdS and ACZTSe materials. The proposed CBTSSe/CdS/ACZTSe structure has a pnp transistor architecture where high band gaps CBTSSe/CdS form the emitter/base junction and ACZTSe acts as low bandgap collector. Using optoelectronic simulations, we investigate the performance of the proposed solar cell and optimize different layer thicknesses to maximize its efficiency. The optimized efficiency of the designed solar cell is found to be 21.63% with 735 mV open circuit voltage, 38.39 mAcm(-2) short circuit current and 76.7% fill factor including Shockley-Read-Hall (SRH), surface and radiative recombination mechanisms. The optimized thicknesses of CBTSSe, CdS and ACZTSe layers are calculated to be 300 nm, 50 nm and 800 nm, respectively. The significance of this HBT solar cell lies in its simplicity of the structure that doesn't require tunneling junction and reduces the number of layers to achieve efficiency comparable to dual junction kesterite solar cells. The design and analysis presented in this article would help in achieving highly efficient inorganic solar cells at low cost and less fabrication complexities.