Innovating Perovskite-Organic Photovoltaics: Towards Surpassing the Detailed Balance Limit

The efficiency of single-junction perovskite and organic solar cells (PSCs and OSCs) has approached the theoretical ceiling defined by the detailed balance (DB) model. To surpass this limit, this thesis investigates hybrid photovoltaic architectures that synergistically integrate perovskite and organic semiconductors. In particular, two emerging configurations, perovskite-organic tandem solar cells (P-O-TSCs) and integrated perovskite-organic solar cells (I-POSCs), are explored as promising platforms to enhance efficiency through spectral complementarity. Three representative studies are conducted to systematically address critical loss mechanisms, spanning from single sub-cell performance to the design of complete tandem and integrated devices. The first study focuses on mitigating voltage losses in wide-bandgap CsPbI2Br PSCs, which are essential for tandem device applications. By introducing Pb(Ac)2 additive, the fabricated champion devices achieve a record-high open-circuit voltage (Voc) of 1.45 V and a power conversion efficiency (PCE) of 16.7%, ranking among the highest reported for CsPbI2Br PSCs at the time. Notably, the Voc of 1.45 V at a bandgap of 1.89 eV corresponds to over 90% of the DB limit, demonstrating substantial suppression of nonradiative losses. To elucidate the origin of energy losses, a stepwise quantification is conducted using photoluminescence quantum yield and quasi-Fermi level splitting measurements on neat perovskite films, partial stacks, and complete devices. The analysis reveals that the dominant nonradiative recombination stems from poor bulk crystallinity and energy-level mismatch at the perovskite/hole transporting layer (HTL) interface. These findings highlight the necessity of concurrently optimizing both the perovskite bulk quality and interfacial energy alignment to approach the radiative efficiency limit, providing clear guidance for the further development of high-performance wide-bandgap PSCs. The second study focuses on mitigating optical losses arising from thin-metal-based interconnection layers (ICLs), a well-known bottleneck in monolithic P-O-TSCs. In conventional designs, the ICLs often incorporate thermally evaporated ultrathin Au deposited atop a MoOx HTL as carrier recombination sites. However, Au exhibits poor nucleation behavior on MoOx, resulting in the growth of large, irregularly shaped nanoparticle clusters that intensify localized surface plasmon resonance (LSPR) effects and significantly diminish near-infrared (NIR) optical transmission. To address this, a novel interfacial engineering strategy is introduced by replacing MoOx with a solution-processable PEDOT:F layer beneath the Au nanoparticles (NPs). The distinct surface energy of PEDOT:F enables the controlled nucleation and growth of smaller, more spherical Au NPs with lower aspect ratios and reduced surface coverage. As a result, LSPR-induced parasitic absorption is effectively suppressed, and optical transmission in the NIR region is substantially improved. When incorporated into two terminal tandem devices comprising CsPbI2Br front sub-cell and various organic rear sub-cell, the optimized PEDOT:F-based ICLs enhance rear-cell photocurrent density (Jsc) by >1.5 mA/cm2, leading to a champion PCE of 25.34%, representing one of the highest reported values for P-O-TSCs. The results emphasize that engineering the morphology of metal NPs is a key strategy for optimizing optical pathways in high-efficiency perovskite-organic tandem architectures. The third study explores interfacial charge transport and recombination in I-POSCs, which eliminate the ICLs used in P-O-TSCs, thereby improving optical transmission and simplifying fabrication. Despite their structural advantages, I-POSCs often suffer from suboptimal charge dynamics at the perovskite/bulk-heterojunction (PVK/BHJ) interface. To unravel these complex interfacial processes, a drift-diffusion simulation framework is developed to systematically capture the influence of interfacial energy-level alignments (including Type I, Type II, and reverse Type II), charge extraction efficiency, recombination kinetics, and carrier mobility on photocurrent extraction, voltage output, and fill factor. This stepwise analysis establishes critical links between carrier transport phenomena and device performance metrics. While Type-II PVK/BHJ alignment promotes photocurrent generation through efficient current extraction, and reverse Type-II alignment preserves photovoltage via beneficial quasi-Fermi level bending, the fill factor becomes the dominant performance-limiting factor in the Type-I transition regime due to moderate energetic barriers. Bimolecular recombination within the organic BHJ is identified as the primary loss mechanism in current I-POSC devices, as opposed to interfacial trap-assisted recombination. Suppressing this recombination channel can lead to substantial performance improvements. However, further predictions indicate that the ideal performance of I-POSCs remains confined within the DB limits of the single-junction OSC subcell. This work provides a unified physical understanding of the unusual behaviors in I-POSCs and offers the I-POSC community clear insights into their true potential. Collectively, these three studies advance a comprehensive understanding of loss mechanisms and interfacial dynamics in perovskite-organic hybrid solar cells. By integrating material engineering, interfacial optimization, and device-level modeling, the thesis outlines concrete strategies to enhance voltage output, reduce optical losses, and improve charge transport. Together, these insights provide practical guidance for the rational design of high-efficiency hybrid architectures and support the continued development of solution-processable photovoltaic technologies toward surpassing the DB limit.