Inert Glove Box Comparison: Perovskite Solar Cell Example
One question to ask yourself when choosing a glove box is what level of inertness do you need? The Ossila Glove Box is compact, easy to set up and maintains a good level of inertness. It does this at a significantly lower cost than more complex, more expensive systems such as Inert or MBRAUN glove boxes. However, this glove box cannot maintain as low moisture and oxygen levels as its pricier competitors... but does that matter?
Device Performance vs. Glove Box
To acheive the highest efficiencies, you should make your perovskite solar cells within a glove box. This is because several components of perovskite devices are sensitive to moisture content and oxygen. Working in an inert environment gives you the best chance of making highly efficient devices. This is often the case for thin film devices, especially if they incorporate small molecules or other air sensitive materials.
Therefore, we use this case study to investigate how inert does an environment need to be for a given process. To do this, we compared the performance of triple-caption perovskite solar cells made in two different processing conditions:
- The Ossila Glove Box maintaining 0.5% O2 content, and <0.75% RH
- Inert glove box at 0.1 ppm levels of O2 and H2O
Some perovskite materials are more sensitive to air than others and triple-cation perovskites (CsFAMAPb(Ix Br1-x )3 ) are particularly robust. We therefore also made triple cation devices in air to provide a full comparison. As expected, all three environments made usable perovskite solar cell devices, but with varying power conversion efficiencies (PCEs). Interestingly, we found no significant difference between device made in the Ossila and Inert glove box, despite the significant difference in price.
The Ossila Glove Box can maintain an environment with less than 0.5% O2 content and moisture levels as low as 15 ppm, while the Inert Glove Box can create inert atmospheres O2 and H2O levels of less than 0.1 ppm. Despite this difference in O2 and H2O levels, there is no significant difference between devices.
Devices made in the our glove box have a slightly lower VOC, but an improved JSC compared to those made in the Inert Glove Box. The devices made in the Ossila Laboratory Glove Box had a champion device efficiency of 19.2%, compared to 19.7% champion for the Inert glove box devices.
This shows that you can fabricate high-performing perovskite solar cells in the Ossila Laboratory Glove Box, just as well as in the much more expensive Inert Glove Box. The levels of >0.5% relative humidity achieved with our glove box are more than suitable for making PSC devices.
Film Quality vs. Glove Box
To investigate further, we characterised perovskite thin films prepared in each glove box with scanning electron microscopy (SEM). The perovskite films made in both glove boxes were extremely similar, with the characteristic uniform grains we expect to see. In contrast, those prepared in air have several pinholes and gaps in the film. This will clearly reduce the charge transfer properties of the perovskite layer, hindering device performance.
The SEM results agree with the X-Ray Diffraction (XRD) and absorption data shown below. In the XRD data, we can see a strong perovskite peak (e.g. at 14 °) for films made in both glove boxes, suggesting there is very little difference in perovskite crystal orientation for films made in either glove box. As expected, these characteristic peaks are strikingly reduced for the films made in air.
We also show normalised absorption profiles for films made in each atmospheric condition. Again, the films in both glove boxes are almost identical, while the films deposited in air have much lower absorption in the visible region and a tail at higher wavelengths.
Different Perovskites in the Ossila Laboratory Glove Box
To further investigate the suitability of our lab glove box for making PSC devices, we made a range of perovskite solar cells. Below is the best and average PSC devices. We are able to make a number of high efficiency PSC devices in the Ossila Glove Box, including MAPbI3 which are notoriously moisture and air sensitive.
| Perovskite | Average PCE (%) | Best PCE (%) |
|---|---|---|
| Triple Cation Mixed Halide perovskite | 16.4±1.8 | 19.0 |
| MAPbI3 | 17.6±1.1 | 19.3 |
| CsFAPbI3 | 14.0±2.0 | 17.0 |
| I301 | 17.3±1.3 | 19.4 |
These performances rival the performances of those made in the Inert Glove Box, proving that extremely highly inert conditions are not necessary for making high efficiency perovskite devices.
Glove Box
