اثر ضخامت لایه انتقال دهنده حفره بر عملکرد سلول های خورشیدی پروسکایتی با ساختار تخت و نانویی

سلول‌های خورشیدی پروسکایت (pscs) به عنوان فناوری فتوولتائیک نویدبخش شناخته می‌شوند، اما افزایش بازدهی آن‌ها به دلیل محدودیت‌های جذب نور و انتقال بار با چالش‌هایی مواجه است. لایه انتقال دهنده حفره (htl) یکی از اجزای کلیدی در بهبود عملکرد این سلول‌هاست که در استخراج حفره، مسدود کردن الکترون‌ها و کاهش بازترکیب در مرز پروسکایت/ الکترود نقش مهمی دارد. این مطالعه با استفاده از شبیه‌سازی اپتوالکتریکی به روش المان محدود، تاثیر ضخامت htl بر عملکرد pscها را با مقایسه ساختارهای تخت و نانوبافت بررسی می‌کند. نتایج نشان می‌دهد که ساختارهای تخت عملکرد پایداری در دامنه وسیعی از ضخامت‌های htl دارند و بهترین بازدهی را در حدود 50 و 350 نانومتر نشان می‌دهند. در مقابل، سلول‌های نانوبافت نرخ تولید حامل را افزایش داده و بهترین عملکرد را در ضخامت‌های حدود 80  نانومتر و 550  نانومتر دارند. با این حال، در ضخامت‌های متوسط، به دلیل تولید غیریکنواخت حامل، کاهش قابل‌توجهی در بازدهی مشاهده می‌شود. این سلول‌ها به صورت مستمر در طیفی از ضخامت‌های htl  از همتایان تخت خود بهتر عمل می‌کنند و در مقایسه با سلول‌های تخت که دارای pce حدود 14% هستند، به مقادیر تا 18%⁓ در 80 نانومتر و 550 نانومتر دست می‌یابند. به صورت مشابه،  برای سلول‌های نانوبافت در حدود ma/cm²  23 به اوج خود می‌رسد، در حالی که برای سلول‌های تخت زیر ma/cm² 20 باقی می‌ماند.  این یافته‌ها بر اهمیت بهینه‌سازی ضخامت htl در طراحی psc ها برای دستیابی به بیشینه بازدهی تاکید می‌کند.

the impact of hole transport layer thickness on the performance of planar and nanostructured perovskite solar cells

1. introductionperovskite solar cells (pscs) are a promising photovoltaic technology due to their high-power conversion efficiency (pce), low-cost fabrication, and tunable optoelectronic properties. achieving optimal performance requires careful design of each layer, especially the hole transport layer (htl), which is critical for hole extraction, electron blocking, and minimizing recombination. htl thickness has a significant impact on charge transport, optical behavior, and overall efficiency. an optimal thickness ensures efficient transport and low recombination, while overly thin or thick layers can lead to shunting or increased resistance and absorption losses. recent research has highlighted the benefits of texturing the perovskite/htl interface to enhance light trapping and charge extraction. however, how htl thickness variations interact with such textured interfaces remains unclear. this study explores the impact of htl thickness in pscs with textured interfaces, showing that combining optimal thickness with interface engineering can substantially boost efficiency. these insights support the development of high-performance, scalable pscs. 2. methodologythis research employs the integration of optical and electrical modules to analyze perovskite solar cells. initially, we utilize the optical module of comsol software to assess the distribution of the electric field. this distribution enables us to derive specifications regarding light intensity, absorption characteristics, and the number of charge carriers present at specific locations within the solar cell. following the input of the initial data into the optical module, we calculate the rate of light-generated electron-hole pair production in the absorber layer. in the electrical module, we investigate the pertinent poisson and continuity equations for electrons and holes, which facilitate the calculation of carrier density and current-voltage characteristics. in the simulation, we employed a planar structure featuring a 200-nanometer-thick perovskite layer as a control sample. subsequently, we performed a comparative electro-optical analysis utilizing a specially designed structure that incorporates sinusoidal nanostructures at the boundaries of all layers, concentrating on the effects of htl thickness. in our prior research, we established that the random sinusoidal texture serves as a more effective geometry for enhancing efficiency in comparison to other structures, such as hillock or pyramidal configurations. unit cells for both planar and nanostructured perovskite solar cells are shown in figure 1. to evaluate the light absorption characteristics of the structures, we conducted numerical analysis using the two-dimensional finite element method (fem). sunlight is modeled as a planar source situated above the structure, simulating the am 1.5 solar spectral irradiance. the wavelength range considered for the absorption spectrum of the cell spans from λmin = 300 nm to λmax = 820 nm. 3. results and discussionthe results show electron-hole generation rates across different wavelengths in each layer of both planar and nanostructured devices. a 2d map of generation within the perovskite layer reveals a uniform distribution in the planar design, with peak generation near the center. in contrast, the nanotextured device displays a more complex and uneven pattern, with significantly higher generation peaks. this indicates enhanced light trapping due to the textured surface. the quasi-sinusoidal texture effectively concentrates absorbed power density, acting like micro lenses that focus light into the active layer and boost local generation rates. shockley-read-hall (srh) recombination analysis for planar and nanostructured perovskite solar cells using cuscn as the hole transport layer (htl) at 80 nm and 600 nm shows a recombination peak near the perovskite-htl interface, with thinner htls shifting it closer to the cell base. the impact of cuscn thickness is evaluated using fill factor (ff), power conversion efficiency (pce), and maximum short-circuit current density (jmax). nanotextured cells outperform planar ones across thicknesses, reaching up to 18% pce and 23 ma/cm² jmax, compared to ~14% and <20 ma/cm² for planar cells. pce and jmax in nanotextured devices show oscillatory behavior, suggesting interference or charge extraction variations due to morphology-induced electric field effects. open-circuit voltage (voc) stays relatively constant (0.82v– 0.92v), with planar cells reaching up to 0.84 v and nanotextured ones up to 0.28 v. ff varies more in nanostructured cells, dropping to 0.72 at 300 nm thickness, while planar cells remain stable (0.82– 0.84). the ff drop in nanotextured cells is likely due to increased surface defects and recombination centers, leading to higher non-radiative losses. 4. conclusionthe thickness of the hole transport layer (htl) plays a vital role in balancing charge extraction and recombination losses in perovskite solar cells. thinner htls (for instance, 80 nanometers) improve charge collection by reducing the distance carriers need to travel. nevertheless, they also heighten recombination at the interface, especially in nanotextured cells, which results in a decrease in the fill factor (ff) and overall efficiency. on the other hand, thicker htls (like 600 nanometers) diminish interfacial recombination by offering greater passivation and a more gradual electric field; however, they may also introduce series resistance that constrains jmax and pce, particularly in planar cells. the noted increase in pce and jmax in nanostructured cells indicates that nanotexturing is a promising method for enhancing light collection, although its advantages are somewhat counterbalanced by increased recombination that becomes more evident at certain htl thicknesses. a thorough examination of the interference effects seen in nanotextured cells, potentially through optical simulations, could yield valuable insights into optimizing htl thickness to achieve the most favorable constructive interference and charge collection. ultimately, hybrid structures that combine nanotexturing with the design of flat interfaces may present an effective strategy to concurrently attain high pce and ff, thus promoting the advancement of more efficient and stable perovskite solar cells.