Organic solar cells (OSCs) have seen a sharp increase in power conversion efficiency (PCE) over the last five years, due to the emergence of Y-series acceptors, a new class of materials . Although carefully tuning device materials can increase PCE, another strategy that can greatly improve performance is tandem cells. This strategy is highly promising, with a Si/perovskite tandem cell reaching 29.8% 2 , the highest PCE for double-junction devices. Although computational efforts are ongoing to optimize single-junction OSCs and predict their efficiencies, there is much less work on tandem OSCs. First, it is still unknown what the maximum theoretical PCE limit is for tandem OSCs with nonfullerene acceptors (NFAs). Shockley and Quisser predicts the limit to be approximately 33% for a single-junction inorganic solar cell , and Vos calculated the limit for a tandem inorganic cell to be 42% under one sun irradiance . Dennler et al. modified Scharber's model and predicted the maximum PCE for tandem OSCs using PC 60 BM as the acceptor to be 15%. OSCs with NFAs as the n-type material are unique with two absorbing materials in each active layer, therefore tandem devices with four unique chromaphores could theoretically exceed these limits.