Inorganic semiconductor compounds, e.g., CIGS and CZTS, are promising materials for thin film solar cells because of their high light absorption coefficient and stability. Research on thin film solar cells using this compound has made remarkable progress in the last two decades. Vacuum-based processes, e.g., co-evaporation and sputtering, are well established to obtain high-efficiency CIGS and/or CZTS thin film solar cells with over 20% of power conversion. However, because the vacuum-based processes need high cost equipment, they pose technological barriers to producing low-cost and large area photovoltaic cells. Recently, non-vacuum based processes, for example the solution/nanoparticle precursor process, the electrodeposition method, or the polymer-capped precursors process, have been intensively studied to reduce capital expenditure. Lately, over 17% of energy conversion efficiency has been reported by solution precursors methods in CIGS solar cells. This article reviews the status of non-vacuum techniques that are used to fabricate CIGS and CZTS thin films solar cells.

The metal plating industry produces a large amount of wastewater generally containing heavy metals with various chemical compounds; as such, treating the wastewater is both an environmental and an economic challenge. A vacuum evaporation system has been developed to effectively reduce the volume of plating wastewater. However, the gas stream discharged from the distillation unit of the evaporator is often contaminated with high concentrations of odorous compounds such as ammonia and dimethyl disulfide (DMDS). In this study, a non-thermal plasma process operated in wet conditions was applied to remove the odorous compounds, and it showed high removal efficiencies of greater than 99% for ammonia and 95% for DMDS. However, the gas flowrate more substantially affected the efficiency of ammonia removal than the efficiency of DMDS removal, because the higher the gas flowrate, the shorter the contact time between the odorous compound and the mist particles in the wet plasma reactor. The analyses of the maximum removal capacity indicated that the wet non-thermal plasma system was effective for treating the odorous compounds at a loading rate of less than 20 mg/m3/min even though the lowest amount of electrical power was applied. Therefore, the wet-type non-thermal plasma system is expected alleviate to effectively abate the odor problem of the vacuum evaporator used in the treatment of plating wastewater.

기존의 재래식 유탕팽화유과의 문제점을 개선하기 위하여 진공을 이용한 진공팽화기를 설계 제작하였다. 공정변수에 따른 진공팽화유과의 특성을 비교 분석하기 위하여 부피팽화율, 밀도, 절단강도, 색도, 미세구조를 측정하였다. 진공팽화기의 공정변수는 가열온도(100, 120, 140, 160, 180oC), 예열시간(0, 2, 4, 6, 8분), 진공팽화시간(5, 10, 15, 20분)이며, 가열온도 100oC, 예열시간 6분, 진공팽화시간 10분에서 진공팽화유과의 부피팽화율은 10.04로 가장 높게 측정되었고, 밀도는 0.15 g/cm3로 가장 낮게 측정되었지만, 부피팽화율 9.47, 밀도 0.16 g/cm3으로 측정된 가열온도 120oC, 예열시간 4분, 진공팽화시간 5분에서의 진공팽화유과가 유탕유과의 외관 및 조직과 가장 유사하였다. 절단강도는 가열온도 100oC, 예열시간 6분, 진공팽화시간 15분에서 140 g/cm2로 가장 낮게 측정되었다. 색도는 예열시간과 진공팽화시간이 증가함에 따라 백색도가 증가하는 경향을 보였고, 황색도는 감소하는 경향을 보였으며, 적색도는 유의적 차이가 없었다. 진공팽화유과의 백색도(L값)가 유탕팽화유과보다 25정도 높았으며, 적색도(a값)와 황색도(b값)는 유의적 차이는 보이지 않았으며, 진공팽화유과의 미세구조는 가열온도 120oC, 예열시간 4분, 진공팽화시간 5분에서 기공이 작고 균일하였다. 유탕팽화유과와 비교 시 절단강도는 유사하였으나, 부피팽화율은 낮았고, 밀도는 높았다. 셀이 균일하게 형성된 진공팽화의 미세구조와는 달리 유탕팽화유과의 미세구조는 표면과 내부층의 차이가 확인되었다. 진공팽화기의 최적 공정조건은 진공팽화유과의 품질을 고려 할 때, 가열온도 120oC, 예열시간 4분, 진공팽화시간 5분으로 판단되었다.