With the aim of achieving high efficiency, cost-effectiveness, and reliability of solar cells, several technologies have been studied. Recently, emerging materials have appeared to replace Si-based cells, seeking economic fabrication of solar cells. Thin-film solar cells (TFSCs) are considered strong candidates for this mission, specifically perovskite-based solar cells, reporting competitive power convergence efficiencies reaching up to 25.7%. Substantial efforts have been invested in experimental and research work to surpass the Si-based cells performance. Simulation analysis is a major tool in achieving this target by detecting design problems and providing possible solutions. Usually, a TFSC adopts p-i-n heterojunction architecture by employing carrier transport materials along with the absorber material in order to extract the photogenerated electrons and holes by realizing a built-in electric field. Eventually, this dependency of conventional heterojunction TFSCs on carrier transport layers results in cost-ineffective cells and increases the possibility of device instability and interface problems. Thus, the design of p-n homojunction TFSCs is highly desirable as an essential direction of structural innovation to realize efficient solar cell operation. In this review, a summary of the fundamentals of TFSC materials, recent design and technology progress, and methodologies for improving the device performance using experimental research studies will be discussed. Further, simulation analysis will be provided by demonstrating the latest research work outcomes, highlighting the major achievements and the most common challenges facing thin film homojunction solar cell structures and the methods to improve them.

Polycrystalline silicon on oxide (POLO) junction passivating contacts have recently been demonstrated as carrier selective contacts for high-efficiency silicon solar cells. The carrier transport through these contacts has been attributed to two competing mechanisms: 1) carrier tunneling through ultrathin oxide and 2) transport through weak spots (pinholes) - the nanoscale regions where oxide thickness has been completely or partially compromised during the processing. In this paper, we use two dimensional device simulations to compare the relative effects of these mechanisms on solar cell characteristics with n-type POLO contact. We show that variation in pinhole areal density (Dph) or the tunnel oxide thickness (tox) both result in qualitatively similar trends in the cell characteristics under dark and light. For a given tox, an exponential variation in results in trends that are similar to those for a linear variation in tox. The effect of pinholes on contact resistance (ρc) and saturation current density (Jo) is most significant for relatively thicker oxides (≥ 2 nm). For tox ≤ 1 nm, ρc and Jo become essentially insensitive to pinholes for Dph < 10¹⁰ cm⁻². The modeling results are compared with a set of published experimental data to predict the possible roles of various mechanisms.

Bifacial technology aims to boost power conversion efficiency of solar cells by effectively harvesting the albedo sunlight reflected from the earth, which is typically uncollected in conventional solar cells. We propose an innovative three-terminal (3-T), four-junction perovskite/silicon bifacial tandem solar cell that leverages albedo to surpass the theoretical limits of the traditional monofacial tandem structures. The cell stacks two identical series-connected double-junction perovskite/silicon tandem cells with a common (middle) terminal such that the bottom tandem cell is integrated upside down to effectively harvest albedo. The albedo absorption in the bottom tandem cell linearly enhances the short-circuit current of the double-tandem structure; hence, it overcomes the classical current-matching limit in series-connected tandem solar cells. We use self-consistent optical/device simulations to investigate the design optimizations of the cell and compare its performance with a conventional tandem structure. With an optimal design, the cell exhibits a remarkable efficiency of 30%-36% (bifacial gain of 10%-30%) for the albedo range of 15%-45%. The 3-T cell design works optimally for any range of albedo that is in contrast with 2-T series-connected cell for which the optimal top cell thickness changes with the value of albedo. Moreover, the proposed cell is relatively less sensitive to the process variations in the perovskite layer thickness. With its remarkable efficiency, which increases linearly with albedo, the proposed cell can be highly attractive for emerging high-efficiency photovoltaic applications.

With the fast progress of solar cells efficiency in the last few years, hybrid organic/inorganic metal halide perovskite solar cells (PSCs) became a center point of research for a lot of solar cell researchers. The perovskite materials show different merits like longer carrier diffusion lengths, wider-tunable bandgap in addition to higher potential of light absorption. The higher efficiency together with the cheaper fabrication methods makes perovskite solar cells comparable with Si-based solar cells. The PSCs efficiency has a remarkable increase from 3.8% to more than 25.2 %. There is a great need for an overall understanding of the function of each of the solar cell components and its impact on cell efficiency and performance. This review starts with the discussion of perovskite structure (electronic and crystal) based on recent research. The working principles and the fabrication methods of PSCs are also introduced. PSCs evaluation is also analyzed and presented with more details regarding modelling approaches and simulation tools.