利用寬頻和全方向性之光擷取層及結構於矽基異質接面太陽能電池

Abstract

本文中，我們利用擁有寬頻與全向性光擷取之微米和奈米結構於矽基異質接面太陽能電池上以提升光伏特性，並且對其光特性及少數載子複合做詳細的討論。 在第一部分，我們利用酸蝕刻與鹼性蝕刻在單晶矽上創作出金字塔/凹槽的復合式結構，並應用在非晶矽/單晶矽之異質接面太陽能電池，藉此提升光萃取以及少數載子生命週期。其太陽能電池的效率達到 15.2%，開路電壓 607 mV，短路電流 36.4 mA/cm2 。此結構可以廣泛的應用在矽晶太陽能電池，對於光電轉換效率的提升有很大的幫助。 在第二部分，我們利用熱氧法製作 SiO 2 層，成功實現 IZO/SiO 2 /Si 所製作成的半導體/絕緣體/半導體的太陽能電池，其轉換效率為 7.01％，開路電壓為 430 mV 以及短路電流 28 mA/cm2 。此外，由於氧化鋅奈米線優越的光捕獲能力，我們進一步將效率從 7.01％提升到 7.51％，短路電流密度從 28.0 增加至 30.8 mA/cm2 。

In this thesis, the broadband and omnidirectional light-trapping scheme employing microscale and nanoscale structures are introduced to Si heterojunction solar cells for boosting the photovoltaic performances, and the optical and carrier recombination characteristics of the devices are discussed in detail. In the first part, hierarchical structures consisting of grooves and pyramids are demonstrated in a-Si/c-Si heterojunction solar cells via isotropic etching followed by anisotropic etching. The structure combines the excellent photo managements and creation of long-lived minority carriers into the solar cells, showing an improved conversion efficiency of 15.2%, an open-circuit voltage of 607 mV, and a short-circuit current density of 36.4 mA/cm2. With the superior omnidirectionality, the enhancement of power generation is up to 92% at high incident angles. Such fabrication approach of hierarchical structures open new avenues for various Si-based solar cells with improved conversion efficiency by effective light harvesting. In the second part, semiconductor-insulator-semiconductor solar cells based on IZO/SiO2/Si can be achieved to the conversion efficiency of 7.01% with a VOC of 430 mV and a JSC of 28 mA/cm2 owing to the optimal SiO 2 layer by 5 minutes hot H2O treatment. In addition, the employment of ZnO Nanorods on IZO/Si heterojunction can improves the Jsc from 28.0 to 30.8 mA/cm2 and the efficiency from 7.01% to 7.51 % due to superior light trapping ability.