Funnily enough, I just recently saw a video about Perovskite solar panels: https://m.youtube.com/watch?v=w2r9_0NxTW8
First time learning about them, but they do seemingly like a great solution once they come into maturity over the next decade. At that point, we could be at only needing ~6% of the Outback to power the world!

Whether you take 1000 AUD to Japan and convert to Yen, or covert 1000 AUD here to USD and then convert that in Japan to Yen, you will end up with the same amount (barring any USD/AUD fluctuations while you travel).
International currency markets are so interlinked that arbitrage opportunities are few and far between.
FWIW, I actually liked the AUD-JPY conversion rate when I went there because it made mental conversion super simple: ¥1000 ~= $10 AUD; their prices are basically just in cents!