有機-無機混合鈣鈦礦從光伏系統至光電化學裂解水的應用與研究

Abstract

有機-無機混合鈣鈦礦因其卓越的光電性質包含在可見光譜範圍內具有良好吸收率、相對較弱的激子束縛能以及微米等級的載子擴散距離，且透過結構離子的更換即可擁有不同大小之能階變化等，使其在許多不同領域上都有很好的發展。 鈣鈦礦太陽電池在短短十年間快速發展將光電轉換效率提升至20%以上，除了鈣鈦礦優異的光電性質外，加上其溶液製程、低成本、易加工性，因而成為太陽能電池領域的明日之星。為了繼續提升元件載子傳輸效能，如何藉由其他傳輸層材料的輔助，提高汲取載子之能力是如今重要的研究內容之一。鈣鈦礦混合路易士鹼添加劑已被證實可以有效提升轉換率，因此本實驗選用尿素作為添加劑，通過加入不同比例的尿素，觀察其表面形貌，最後成功降低鈣鈦礦吸光層中的缺陷，並提升元件效率。接著，引入介面改質材料使鈣鈦礦吸光層產生之激子能夠更快速的分離為載子，並經由傳輸層傳輸分離，減少載子再結合的機率。本實驗使用碳60-吡咯烷三羧酸(CPTA)披覆於氧化錫表面，通過CPTA的氫氧官能基和氧化錫中含有氧空缺缺陷之錫原子進行鍵結，以達到更佳的載子傳輸能力，進一步提升太陽能元件之光電轉換效率。 太陽能的間歇性要求開發系統來存儲多餘的能量，發展利用光電化學（PEC）水分解為氫氣和氧氣的形式儲存，其可再生性、可持續性以及環境友善等特性，被視為另一種解決能源危機最有希望的方法之一。以往金屬氧化物由於其長期穩定性而被廣泛的作為PEC水分解光陽極進行研究，但是較大能隙的金屬氧化物不能充分吸收可見光區域的波長，因此造成較低的光電流。而由於鈣鈦礦具有能隙工程和吸收各種波長的潛力，能夠取代金屬氧化物應用在光電化學分解水方面。本實驗初步架構將鈣鈦礦太陽能電池浸泡在水溶液中通過陽光將水直接分解為氧氣和氫氣之光電化學系統，並利用保護層對鈣鈦礦太陽能電池進行保護，提升在溶液中的穩定性，接著嘗試利用電化學沉積的方式成長鎳-鐵層狀雙氫氧化合物作為催化劑，觀察不同電位成長之鎳-鐵層狀雙氫氧化合物表面形貌，透過線性掃描安伏法進行量測，有效降低起始氧化電位，並提升光電流。

Organic-inorganic hybrid perovskites have been well developed in many different fields due to their exceptional optoelectronic properties such as remarkably high absorption over the visible spectrum, low exciton binding energy, long charge carrier diffusion lengths in the μm range, and a tuneable bandgap by interchanging various structure ions. Perovskite solar cells (PSCs) have drawn enormous attention in recent years owing to their high power conversion efficiency over 20%. In addition to the excellent photoelectronic properties of perovskite, solution process, low cost, and low temperature synthesis, which make it a rising star in the field of solar cells. In order to promote carrier transmission efficiency of devices, how to elevate the ability of quenching carriers via aiding with other transport layers’ is one of the important issues nowadays. Perovskite added Louis base has been proven to facilitate power conversion efficiency of perovskite solar cells; therefore, urea is adopted as an additive. Through observation of the surface morphology with different proportion of urea in perovskite, finally the defects in the light absorption layer were successfully reduced, further enhances the efficiencies of devices. After that, our research is introducing the surface modification material to effectively separate excitons into carriers, then quench by electron transport layer (ETL), reducing the probability of carrier recombination. Here, C60 pyrrolidine tris-acid (CPTA) is passivated on the surface of tin oxide (SnO2), the hydroxyl terminal groups on CPTA are coordinated with oxygen-vacancy-related defects of Sn in SnO2, and chemical bonding with interface modification brings better transfer ability, further improves the performance of perovskite solar cells. The intermittent nature of solar energy requires the development of systems to store excess energy, thus advance of photoelectrochemical (PEC) water splitting into hydrogen and oxygen, which is renewable, sustainable, and environment-friendly, has been regarded as one of the most promising candidates for solving the energy crisis. In the past, metal oxides have been extensively researched as PEC water splitting photoanodes due to their long-term stability, but a metal oxide with a large band gap possesses a low photocurrent, as it is unable to sufficiently absorb the wavelengths of the visible light region. However, perovskite as a substitute for metal oxide, due to its potential for bandgap engineering and absorbing various wavelengths, which can apply to photoelectrochemical water splitting. Here, our research preliminary set up a photoelectrochemical system which immerse a perovskite solar cell in aqueous solution to decompose water into oxygen and hydrogen through sunlight. Moreover, utilize protect layer to prevent the solution from invading into the perovskite solar cell, to increase the stability in the solution. Use electrochemical deposition to grow Nickel-Iron layered double hydroxides (Ni-Fe LDH) as a catalyst afterwards. By means of linear sweep voltammetry measurement and the observation of surface morphology of Ni-Fe LDH grown at different potentials, found that the Ni-Fe LDH can effectively reduce the onset potential and increase the photocurrent.