Perovskite and copper indium gallium selenide: A wonderful marriage for tandem photovoltaics with efficiency approaching 30%

Tandem solar cells (TSCs) represent an attractive technology that can overcome the single-junction Shockley-Queisser limit. Recently, a tandem structure combining wide-bandgap metal halide perovskite with complementary bandgap copper indium gallium selenide (CIGS) photovoltaic technology has demonstrated a realistic pathway to achieve the industrialization goal of pushing power conversion efficiency (PCE) approaching 30% at low-cost. In this review, we first pinpoint the unique advantage of perovskite/CIGS tandems with respect to the other mainstream photovoltaic technologies and retrospect the research progress of perovskite/CIGS TSCs from both PCE and stability perspective in the last years. Next, we comprehensively discuss the major advancements in absorbers, functional layers of the individual sub-cell, and the interconnection layer between them in the recent decade. Finally, we outline several essential scientific and engineering challenges that are to be solved toward the development of efficient, long-term stable, and large-area perovskite/CIGS TSCs in the future.